Usage:

logging_subprocess_example.py

#!/usr/bin/env python3

import logging
import subprocess
import tempfile
import sys

# Set-up logging to both console and a file log.
logger = logging.getLogger()
logger.handlers = []
logger.setLevel(logging.DEBUG)

# Console logging will be only INFO or higher
# This could be configured for CLI invocations
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.INFO)
console_handler.setFormatter(
    logging.Formatter('%(asctime)s %(levelname)-8s %(message)s')
)
logger.addHandler(console_handler)

# Adds log file handler. Everything DEBUG or higher is logged here
# You could potentially have 1 log per benchpress invocation
file_handler = logging.FileHandler(filename='benchpress.log')
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(
    logging.Formatter(('%(asctime)s '
                       '%(filename)s:%(lineno)d %(levelname)-8s %(message)s'))
)
logger.addHandler(file_handler)

# If you want to keep per-command log files, instead
# of using temp files, you could give them a proper name and path.
with tempfile.TemporaryFile() as temp_stdout, \
     tempfile.TemporaryFile() as temp_stderr:

    cmd = sys.argv[1:]  # bad practice, only use for cmd
    process = subprocess.Popen(cmd,
                               stdin=subprocess.PIPE,
                               stdout=temp_stdout,
                               stderr=temp_stderr)
    process.wait()

    temp_stdout.seek(0)
    stdout = temp_stdout.read().decode('utf8', 'ignore')

    temp_stderr.seek(0)
    stderr = temp_stderr.read().decode('utf8', 'ignore')

    status_code = process.returncode

    output = '\nstdout:\n{}\nstderr:\n{}\nstatus_code: {}'

    # Imaging this is the parser call
    msg = output.format(stdout, stderr, status_code)

    # Here we log to log file only
    logging.debug(msg)

    # Here we log to console and log file
    logging.info('cmd: {}\n'.format(cmd) + msg)